I came to this book after reading about it in Jane Austen's 'Northanger Abbey', which I suspect is why many enquirers are now reading this! I really enjoyed it and, although some of the other reviewers' negative comments are at least partly justified, I'd say, if you're not afraid of long novels, give it a go, it's just good fun.
By 21st century standards of horror, this story is tame and childish, but if you're like me and don't appreciate the excesses of modern horror and supernatural/occult things, but just enjoy a good read, you'll find this more to your taste. Yeah, sure there are some unbelievable parts, (like Emily's being able to compose whole sonnets on the spot, for one), but fiction like this is not really meant to be convincing. Mrs Radcliffe wrote to entertain the masses, and that's what she achieves. Yes, the desciptions can be a bit tedious at times, but if you read quickly as most of us do when we're 'in to' a novel, they soon pass and you get on with the story.
I esp. liked the fact that all the mysteries are explained in the end which saves you from having to go through the dissatisfying experience of wanting to know exactly what happened back there when 'x' did 'y' and so on, but never being told. (I sometimes wonder if some authors couldn't think of anything convincing with which to tie up their loose ends!!)
Have fun!=)